This invention relates to a method of recovering alkoxyketone compounds having a high degree of purity from a mixture of an alkoxyketone compound and the corresponding 1-alkoxy-2-alkanol compound.
The most common form of preparing alkoxyketone compounds is to catalytically dehydrogenate the corresponding 1-alkoxy-2-alkanol compound in the vapor phase. When such a preparative method is used, problems of separation arise. The difficulties surrounding the separation of an alkoxyketone compound from admixture with the corresponding 1-alkoxy-2-alkanol have been primarily due to the formation of a binary azeotrope composition.
This difficulty has been noted in the past and a variety of solutions have been proposed in an attempt to obtain alkoxyketone compounds of high purity. Heretofore, the separation has been effectuated either by chemical modification followed by distillation or by multistep azeotropic distillative methods. For example, U.S. Pat. No. 2,170,855 discloses a chemical modification method in which an organic acid or anhydride is added to a reaction mixture of an alkoxyacetone compound and the corresponding 1-alkoxy-2-propanol compound resulting in the formation of the high boiling ester derivative of the 1-alkoxy-2-propanol starting material. The resulting mixture is distilled and redistilled to recover the desired alkoxyacetone.
Alternatively, U.S. Pat. Nos. 2,795,873 and 3,525,735, respectively, discloses azeotropic distillation processes in which either an unsubstituted monohydric alcohol or water is added to the reaction mixture in order to break the minimum boiling point binary azeotrope. In these processes, a new lower boiling binary azeotrope is formed between the azeotropic solvents and the alkoxyacetone compound which may then be removed from the binary azeotropic mixture by distillation.
Although, they seem relatively simple and efficient, the prior art processes suffer from one or more inherent limitations and disadvantages. For example, it is generally recognized that both of the previously disclosed processes usually give rise to alkoxyketone compounds that are contaminated with unacceptable amounts of the corresponding 1-alkoxy-2-alkanol compound. In addition, the azeotropic distillation process requires large expenditures of energy due to the very high latent heat of the azeotropic solvents, as well as, time consuming and cumbersome purification procedures to remove the desired alkoxyketone compound from the azeotropic solvent. Consequently there exists a need for a fast and more efficient single step process for separating alkoxyketone compounds from the corresponding 1-alkoxy-2-alkanol compound with enhanced purity of the alkoxyketone compound coupled with low energy requirements.